Computer power consumption

In a previous post, I promised to measure the power consumption of my PCs. I finally did this, and got the following results:

Computer off, power supply off: ......... 0 Watt
Computer off: ........................... 7 Watt
Windows idle after startup: ............ 64 Watt
Book generator running: ............... 112 Watt
Monitor (Flatscreen) alone: ............ 36 Watt

This result was slightly surprising for me. I would have expected my PC to use more power than 112 Watt when running Cake - after all, it is using the CPU fully and also using the harddisk quite a bit. What are all these 350 Watt power supplies for, I wonder? The result also changes my checkers programming economics post: My book generator now "only" uses 2.7kWh per day, or 0.35$ a day. Since I have been computing opening books for about 4 years now, that puts the worth of the opening book at 500$.
On the other hand, 112 Watt is still a lot, given that we should be moving towards the 2000-Watt-Society - I am using over 5% of my power consumption for something rather useless like checkers book building....

I also measured the power consumption of my other PCs. Unsurprisingly, my other desktop PC is quite similar to the book generator PC, while my old laptop with a 1.4GHz Centrino processor uses only 23.5 Watt idle and 39 Watt when running Cake. Turning off the LCD screen saves another 6 Watt. Here's an interesting thing: on my desktop PC (with a AMD 64 3400+), running Cake costs about 50 Watt more compared to the idle state of the PC for nearly 2000 kN/s. On my laptop, running Cake at about 70% of that speed costs only 15 Watt, or about 3 times less. That means that my laptop is producing about twice as many nodes/second with the same amount of energy. Unfortunately, I measured these numbers before I got my new Core Duo machine, so I have no figures for that.